For Colt Government, Combat Elite, Delta Elite, Officers ACP, and Combat Commander automatic pistols with factory original fixed sights. The professional gunsmith must use the available special Trijicon staking tool. This staking tool will fit both .125 and .055 tang widths. Other staking tools will destroy these blades and cannot be used. The .125 tang width blade can be modified by a local gunsmith to .085 to fit a Springfield 1911, but other .45 brands don't fit these blades. An A2 post will fit on an A1 rifle.